The transition is slow? You are probably on Firefox. Firefox is not as smooth as the others. Safari is the smoothest, then comes Chrome, then IE, and Firefox is a little choppy. In my experience I believe there is nothing that can be done because that is how Firefox is built.
Testing with Firefox on Mac I have almost no lag, but on Windows it looks a bit choppy as you described.
If you want you can change the reveal effect in the Admin CP from Effect.BlindDown to one of the other effects that will not lag in any browser.